Possible Clues:

• Nuclear reaction
• Splitter hearing what remains of traditional fare, 18 28
• Reproduction by dividing
• See 17 across.22 Perhaps Pa did not continue with this because it was too old
• Atomic energy source
• Splitting (of e.g. nucleus)
• Splitting of atom
• Energy producer
• By the sound of it, angling in the nuclear age
• So is fin (anag.)